The Space Shuttle Program Zero
Base Cost Study was a key Shuttle cost study of the early 1990s. This study was at the front end of numerous
studies to follow addressing what was to come
after the Space Shuttle. These 2 charts below are some of
the more significant pieces of information when trying to
understand the evolution of human space flight
technology, infrastructure and business processes.

1:
Do NOT confuse a Zero Base amount with
yearly costs, required budget or
expense amounts any given year for achieving
a certain number of flights, as utilization in any given
year may or may not alter actual costs, required budget
amounts or total expenses. For example, if planning on 5
flights, but making only 4, the dollar difference is
actually manifest not as a savings but as simple
under-utilization due to unforeseen events. The
difference would likely still exist as a cost, have to be
budgeted for and expensed at the flight rate
of 5. Hence, a Zero Base concept goes hand-in-hand closer
to the notion of "steady states" over many
years or capacities maintained or targeted on a steady
basis.

2:
Do NOT confuse a Zero Base concept with that
of fixed costs. The Zero base assumes that
the capability exists only for the indicated number of
flights and workforce, facility, equipment, flight or
ground, is not a cost if it is not required to achieve
the indicated flight rate. For example, if at a flight
rate of 3 only 2 Orbiter Processing Facilities (OPF) are
required, rather than the 3 that exist, the values shown
for a flight rate of 2 do not include any costs with the
3rd OPF. This was stated in the study as:

At low flight rates, when
facilities or vehicles are not needed to support the
flight rate, they are not maintained

No cost included for retention
of capability to increase flight rate capability at a
later date

No OMDPs performed on orbiter
vehicles not required to meet the steady state flight
rate

For each flight rate case, that
flight rate is the assumed steady state flight rate
for all future years

However, in
general a lower number compared to 100 units in the
column for a steady 6 flights per year would likely
indicate a higher fixed cost if that value were to be
studied separately. Example  a 119.3 in column 6
would indicate a stronger fixed cost behavior
there than in a column 6 with a value of 135.2. This
reflects on the issue of the NASA Space Shuttle, or such
related architecture, workforce, business process, and
business technology fixed costs.

3:
How to read this table? Example 1 - there is no
difference in cost that can be found at the Michoud
Louisiana External Tank (ET) Manufacturing site between
having a production capacity of 1, 2, 3 or 4 ETs,
but if the capacity for manufacturing 5 tanks in a year
were targeted and maintained that cost would be 4.2%
higher than the capacity cost compared from 1 to 4 tanks
a year. Example 2  If mission operations at the
Johnson Space Center (JSC) cost 100 units to
have a capability to launch the Shuttle once per year,
then to launch twice per year on a steady state basis
would be 4.1 % more.